This application relates to performance lighting and, more specifically to an improved control system for fixtures capable of varying beam parameters during use.
Performance lighting systems have long employed large numbers of fixtures each selected and adjusted to produce a beam of a particular size, shape, and color aimed at a fixed location on the stage. The only beam parameter variable during the performance is intensity, and the character of the lighting effect onstage is adjusted solely by changing the relative intensities of the variety of fixtures provided.
The advantage of this "one function/one fixture" approach is its use of relatively low technology hardware involving no moving parts and hence relatively high reliability and simple maintainance. The disadvantage is the need for many more fixtures than are used at any one time--or would be required if the fixtures were capable of varying other beam parameters during the performance. There is the direct cost to buy or rent the large number of fixtures required plus their associated supporting structure, dimming equipment, and interconnecting cables as well as the time and labor required to install, adjust, and service this amount of equipment.
It has long been apparent that were fixtures able to change beam parameters in addition to intensity (like color, beam size, or even azimuth and elevation), either as the result of integral remotely actuatable mechanisms and/or devices (like color changers) which may be retrofitted to conventional fixtures, then lighting effects could be varied by actually changing the fixtures' beams rather than dimming between otherwise identical fixtures with different fixed adjustments--requiring fewer fixtures to produce a given lighting design with consequent savings.
Each such "multi-variable" fixture could, over the course of the performance, duplicate the results it currently requires many fixtures to achieve--as well as adding dynamic changes in the beam to the lighting effects possible
The viability of employing fixtures with remotely adjustable beam size, color, shape and/or angle as a method of reducing system size depends upon a control system, first disclosed in U.S. Pat. No. 3,845,351, capable of storing absolute desired parameter values for each of the controlled parameters in each of the desired lighting effects and of automatically conforming the fixture's incrementally adjusted beam varying mechanisms to those values.
Similar systems were subsequently disclosed in U.K. Pat. No. 1,434,052 and U.S. Pat. No. 4,392,187, and today, the rental of such systems to concert, television, and theatrical productions is a multi-million dollar industry.
There have, however, been unexpected difficulties with developing a truly practical embodiment of such a control system.
Two approaches have been employed:
One, represented by the Vari-Lite.TM. system (of Vari-lite, Ltd., Dallas, Tex.), as disclosed in U.S. Pat. No. 4,397,187, employs completely custom hardware and software.
Any such custom control system is very expensive because the number of such systems built relative to even the limited number of conventional lighting memory consoles produced is very small. No significant volume cost reductions are possible and the considerable investment in the "ground up" development of a specialized control system handling up to eight times the amount of data per fixture (relative to a conventional console) can be amortized across only a limited number of units.
Further, it is inevitable that the features and controls provided by any specialized controller will not meet the requirements of all users, and that changes will be requested by users over time. This requires a further investment by the manufacturer in hardware and software revisions, amortizable across the same relatively limited volume.
It had also been widely assumed that remotely adjustable devices (whether color changers, remote yokes, or multi-variable fixtures) would be used on an exclusive basis to maximize the purported gains in system efficiency. Due to a variety of factors including the high cost of such equipment, it has instead been the case that the number of such devices per system may vary widely and that, contrary to expectations, devices of several different types (such as both color changers and remote fixtures) may be employed in the same system, together with conventional fixtures and their controllers.
These "real world" conditions further complicate the development of a suitable memory system, for the unit must be capable of economically driving a handful of such devices or dozens or even hundreds. Clearly, it is difficult to design a single control system capable of varying its memory capacity and outputs over a range of 10:1. Therefore, competing at both ends of this range of applications may require the use of an "overqualified" control system for smaller numbers of fixtures and/or two or more control systems for the large ones. The only alternative is the development of different models of the same control system with a consequent increase in development cost.
It should also be noted that the 10:1 range in the number of controlled devices required by the applications for such equipment also requires an equally flexible method of reliably distributing the necessary data. While the use of multiplexed data links for this purpose has long been known, the inherently higher data rates of multi-variable control systems requires either multiple data links of limited capacity (with a variety of practical drawbacks) or a single data link capable of extremely high data rates without EMI susceptability.
Further, as the control system is optimized for a given controlled device, driving dissimilar devices or major revisions of the same device may be difficult or impossible. Once the commitment has been made to a given control structure and data transmission means, changes in the design of the controlled device which require that additional or different data be stored and transmitted may require an expensive revision of the control system as a whole and/or may render the encoded data on the data link between the control system and the controlled devices incompatable with existing decoder hardware.
This "upwards-incompatability" and lack of "cross-compatability" with other remote devices, are an impediment both to the user (in requiring multiple control systems and operators to attempt to synchronize the different remote devices) and to the manufacturer (in increasing the cost of the revisions required to maintain competitiveness). Such systems will also suffer from further disadvantages when features requiring more sophisticated data manipulation such as the conversion of absolute beam location data to required azimuth and elevation are sought. Because the control system operates on a time-shared basis among the various controlled devices, a relatively modest number of machine cycles required by a given feature must be multiplied by the number of controlled fixtures. The total increase in processor workload may exceed the remaining processor "overhead" and an expensive and time-consuming change of processors may be required.
The second approach to the construction of such systems, typified by the Pana-Spott.TM. multi-variable fixture (of Morpheus Lights, San Jose, Ca.), does not employ a custom control system, but instead configures the fixtures to allow use of any conventional lighting memory console, such as disclosed in U.S. Pat. No. 3,898,643.
Specifically, the inputs to the Panaspott.TM. remote fixture are configured to accept 11 parallel 0-10 volt DC outputs as produced by any standard lighting control console; four employed for analog values (azimuth, elevation, beam size and intensity) and seven employed for essentially single-bit digital values (representing the in/out condition of each of the seven frames in the color changer).
The use of a modern memory controller provides a variety of sophisticated features including a CRT, keyboard, data carrier, and cue manipulations without the development costs which attend the creation of a custom controller. There have, however, been several severe drawbacks to the use of such stock consoles
One is relative cost. Given the need for storing only one fixture variable and the fact that it is generally desirable for multiple fixtures to share the same discrete output, one $22,000 console generally suffices for a system of 300 conventional fixtures, representing a front-end control cost of only $70 per fixture. In the case of the Panaspot.TM., eleven discrete outputs are required for each fixture and, by definition, such fixtures achieve their benefits only if each fixture's inputs are discrete outputs of the console.
Therefore one $22,000 console is required for each eleven remote fixtures for a front end control cost of $2000 per fixture. The number of fixtures controlled per console can be increased by using the same console output as an input to more than one fixture, but this limits the versatility of the fixtures and, in so doing, erodes the justification for their use.
The use of stock lighting consoles for this purpose has also proven to present severe operational disadvantages relative to a custom controller.
Because the "stock" controller's benefits derive from use of a standard lighting control product optimized for cue-to-cue intensity operation, the operator is also required to use input devices and data display formats which are not designed for multi-variable fixture control.
While such a console records and displays the variables for each fixture, all variables for all fixtures are presented uniformly as two numbers: the channel number and a percentage value. A time consuming reference to a list or table is required to determine that the beam size for fixture #8 is controlled by channel #93. Conversely, the CRT display of values is useless without conversion.
Further, such consoles generally provide input devices allowing manual or keyboard adjustment of only a single output or group of outputs at a time. Therefore, most recording operations for remote fixtures require a lengthy series of adjustments, with reference to a table of 100 or more functions between each one.
Such consoles also do not provide data manipulation features unique to multi-variable fixture use, nor can their outputs be reconfigured to provide resolutions greater than or less than 8-bits.
One might suggest modifying the standard memory controller with more appropriate input devices, display modes, outputs, and software, but that contradicts the whole purpose of using an existing controller. Further, such modifications would require the participation of the console manufacturer, either in performing the actual modifications or in providing the documentation to the fixture manufacturer or a third party necessary to do the work. The major dimming equipment manufacturers have made it clear that the size of the market for such modifications does not justify their participation.
A practical control system for remotely-adjustable fixtures therefore requires the development of a new control system approach providing: input devices suited to the needs of the controlled fixture; shared portions of the system of minimum cost; economical operation from a few units to several hundred; a data link capable of handling the maximum data rate reliably, yet inexpensive to decode; capable of mixing various types and generations of controlled device on the same system without modification; capable of modification to meet user requirements at minimal cost.
It is the object of the present invention to provide an improved control system for multi-variable fixtures meeting these requirements.